let _Vue = null
export default class VueRouter {
  static install(Vue) {
    //1 判断当前插件是否被安装
    if (VueRouter.install.installed) {
      return;
    }
    VueRouter.install.installed = true
    //2 把Vue的构造函数记录在全局
    _Vue = Vue
    //3 把创建Vue的实例传入的router对象注入到Vue实例
    // _Vue.prototype.$router = this.$options.router
    _Vue.mixin({
      beforeCreate() {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router
        }
      }
    })
  }
  constructor(options) {
    this.options = options
    this.routeMap = {}
    // observable
    this.data = _Vue.observable({
      current: "/"
    })
    this.init()
  }
  init() {
    this.createRouteMap()
    this.initComponent(_Vue)
    this.initEvents()
  }
  createRouteMap() {
    //遍历所有的路由规则 吧路由规则解析成键值对的形式存储到routeMap中
    this.options.routes.forEach(route => {
      this.routeMap[route.path] = route.component
    });
  }
  initComponent(Vue) {
    Vue.component("router-link", {
      props: {
        to: String
      },
      render(h) {
        return h("a", {
          attrs: {
            href: '#' + this.to
          },
        }, [this.$slots.default])
      },
      // template:"<a :href='to'><slot></slot><>"
    })
    const self = this
    Vue.component("router-view", {
      render(h) {
        // self.data.current
        const cm = self.routeMap[self.data.current]
        return h(cm)
      }
    })

  }
  initEvents() {
    window.addEventListener('hashchange', this.onHashChange.bind(this))
    window.addEventListener('load', this.onHashChange.bind(this))
  }
  onHashChange () {
    this.data.current = window.location.hash.substr(1) || '/' 
  }
}